Mare Moscoviense ("Sea of Moscow") is a lunar mare that sits in the Moscoviense basin. It is one of the very few maria on the far side of the Moon. Like Mare Marginis, this mare appears to be fairly thin. However, it is clearly centered within a large impact basin. It is also much lower than either the outer basin floor or the farside highlands. At the center of the basin (or the southwest portion of the mare) is a mascon, or gravitational high. (from Wiki)